No official rules but do not two people ware only one bubble football suit.

4. what is the size?

typically, three sizes:

S : 1.2M 1M ( 4′ Dia 3.3′ )

M:1.5M 1.3M (5′ Dia 4.3′ )

L : 1.7M 1.5M (5.6′ Dia 5′ )

5. can I add my own logo

Yes and it is free.

6. Any dangerous?

Much safer than normal soccer/football

7. can I cancel my order?

No, after you payed, you can not cancel it.

For the One Year Warranty:

The ball come with 1 Year Warranty for customer deficiencies (you are responsible for all shipping). For manufacturer deficiencies, we will re-ship new one instead if the ball is under the condition of normal use.After the warranty expires or for non-covered damages to ball, we are able to repair ball at a fraction of the cost of new ball.